Known in the art is a heat-transfer device disclosed in U.S. Pat. No. 3,986,550 which can be used as a heating device, as well as for removing heat when cooling various objects.
The known heat-transfer device comprises evaporation and condensation chambers made in the form of tanks, the space of the evaporation chamber, having liquid and vapour zones, is communicated with the space of the condensation chamber through a vapour-flow branch pipe and a fluid-flow branch pipe. For simplicity, these branch pipes will further be called as respectively, "vapour-flow branch pipe" and "fluid-flow branch pipe".
When heat is supplied into the evaporation chamber a liquid heat carrier is evaporated. The evaporated heat carrier is evaporated. The evaporated heat carrier through a vapour-flow branch pipe is admitted into the condensation chamber, where it is condensed giving the latent heat of evaporation to the object being heated. The condensed heat carrier flows into an evaporator through the fluid-flow branch pipe.
Due to the fact that in the known heat-transfer device the condensation chamber is made in the form of a tank, in which the length-to-diameter ratio is close to unity, this device cannot be used for heating of extended and horizontally located objects.
A heat-transfer device is known, which is desribed in the paper by E. W. Saaski J. C. Hartl, A High Performance Cocurrent-Flow Heat Pipe for Heat Recovery Applications" AJAA Paper 1980, v.1508.
The known heat-transfer device can be used for heating of extended objects located vertically or with a positive angle of inclination to the horizon.
The known heat-transfer device comprises an evaporation chamber whose space has vapour and liquid zones and a condensation chamber made in the form of a pipe-line provided with a partition mounted in the space along its longitudinal axis and used for directing the vapour into the space of the condensation chamber as well as for its returning the condensed liquid into the evaporation chamber.
The space of the condensation chamber is connected with an evaporation chamber through a fluid-flow branch pipe immersed into the liquid heat carrier.
In the known device the heat carrier vapours from the evaporation chamber are fed upwards into the condensation chamber, where they are condensed while passing along the longitudinal partition. A larger part of the condensed heat carrier returns by gravity into the condensation zone through the fluid-flow branch pipe.
The known device can be used for heating rather extended objects only if they are vertical and mounted at a positive angle of inclination of the device to the horizon because in this case reliable return of the condensed heat carrier into the condensation chamber is provided by gravity. With negative angles of inclination of the device to the horizon, when the evaporation chamber is located above the condensation chamber, the above-mentioned device is inoperative, because in this case the liquid heat carrier flows into the condensation chamber and the evaporation chamber is dried.
The operational efficiency of the given device with a horizontal arrangement is not high, because in this case, in the first place, only a portion of the inner surface of the evaporation chamber is covered by liquid heat carrier resulting in a decrease of the thermal power supplied to the evaporation chamber, and, in the second place, the liquid heat carrier covers a portion of the heat-transfer surface in the condensation chamber as a thick layer, and this also reduces the transmitted thermal power.
Furthermore in the case of the horizontal arrangement of the device, any increase in the length of the condensation zone with its low diameter results in formation of a stagnant zone at the end of the condensation chamber opposite to the evaporation chamber. The cooled liquid heat carrier, which does not take part in the "evaporation-condensation" process, will be accumulated in this stagnant zone. Therefore, the above-mentioned heat-transfer device can be used for heating only horizontally arranged objects having a small length and requiring a low thermal power.
A disadvantage of the known device is that it cannot be used for heating of extended, horizontally disposed objects.
Also known a heat-transfer device disclosed in U.S. Pat. No. 4,050,509, which can be used for heating of foundation of a roadbed by solar energy.
The known heat-transfer device comprises an evaporation chamber with at least one heating source. The space of an evaporation chamber is divided into a liquid zone and a vapour zone. The condensation chamber is located below the evaporation chamber and is made in the form of a pipeline, in the space of which along its longitudinal axis there is located a tube whose inner space is communicated with the spaces of the condensation and evaporation chambers. The tube is used for supplying vapour into the space of the condensation chamber and for returning the condensed liquid into the evaporation chamber.
The known heat-transfer device operates as follows. When heat is supplied to the evaporation chamber, the liquid heat carrier is evaporated and is fed through the pipe into the space of the condensation chamber. In this space the vapours of the heat carriers are condensed and the latent heat of evaporation is transferred to the object being heated. The process of heat transfer to the heated object is effected until the liquid heat carrier in the evaporation chamber is completely evaporated and the pressure in this chamber drops down. From this instant transfer of heat to the object being heated is stopped, while the liquid heat carrier is forced from the space of the condensation chamber into the evaporation chamber through the tube lowered under the level of the liquid heat carrier. This process is effected due to excessive pressure of the noncondensed gases in the space of the condensation chamber. As the liquid heat carrier is being forced from the condensation chamber to the evaporation chamber, the pressure in the condensation chamber drops down, while in the evaporation chamber the pressure increases due to evaporation of the liquid heat carrier fed into this chamber. When the pressure in the evaporation chamber exceeds that in the condensation chamber, the process of heat transfer to the heated object is renewed. This device is operative at a vertical arrangement of the condensation chamber or at angles of inclination close to vertical.
If the condensation chamber is placed horizontally, its heat transfer surface is considerably reduced, because only the upper half of the condensation chamber serves as a heating surface, because the lower half is filled with liquid heat carrier all the time. As a result, the transmitted thermal power is reduced. The thermal power transmitted is also reduced due to the required decrease in the velocity of the vapour flow in the tube so that the liquid heat carrier is capable of flowing from the condensation chamber into the evaporation chamber by gravity.
Thus, the known heat transfer device has the following disadvantage: it cannot be used for heating extended horizontally located objects with a magnitude of the transmitted thermal power equal to a few kilowatts and a relatively high ratio of the length of the condensation chamber to its diameter equal to 200-400 and higher.